Storage stable aryl nitrone compositions

Abstract

Aryl nitrones, of the type used in contrast enhancement photolithography techniques, are stabilized by adding thereto a drying agent such as molecular sieve, silica gel or an alkylalkoxysilane. The resulting compositions are substantially storage stable.

What is claimed is: 
     
       1. A composition comprising at least one aryl nitrone and a drying agent which is substantially inert to said aryl nitrone. 
     
     
       2. A composition according to claim 1 which also comprises a solvent suitable for use in providing a spincoatable mixture. 
     
     
       3. A composition according to claim 2 wherein the drying agent is a molecular sieve, silica gel or an alkylalkoxysilane of the formula (R 7 ) m  Si(OR 8 ) p , wherein R 7  and R 8  are lower alkyl radicals and m+p=4. 
     
     
       4. A composition according to claim 3 which also comprises a substantially inert polymeric binder. 
     
     
       5. A composition according to claim 4 wherein the aryl nitrone has formula II in the drawings, wherein: Z is (R 3 ) a  --Q--R 4  -- or R 5  ;   Q is a monovalent, divalent or trivalent substituent or linking group;   each of R, R 1 , R 2  and R 3  is independently hydrogen, an alkyl or substituted alkyl radical containing 1-8 carbon atoms or an aromatic radical containing 6-13 carbon atoms;   R 4  is an aromatic radical containing 6-13 carbon atoms;   R 5  is an aromatic heterocyclic radical containing 6-20 carbon atoms in which the hetero atoms are at least one of oxygen, nitrogen and sulfur;   R 6  is an aromatic hydrocarbon radical containing 6-20 carbon atoms;   X is halo, cyano, aliphatic acyl, alkyl or substituted alkyl or 1-8 carbon atoms, aryl of 6-13 carbon atoms or carbalkoxy;   a is from 0 to 2;   b is from 0 to 3; and   n is from 0 to 4.   
     
     
       6. A composition according to claim 5 wherein R 2  is hydrogen, R 6  is phenyl and Q is F, Cl, Br,I, O, S or N. 
     
     
       7. A composition according to claim 6 wherein the nitrone is α-(4-diethylaminophenyl)-N-phenylnitrone. 
     
     
       8. A composition according to claim 7 wherein the drying agent is a molecular sieve. 
     
     
       9. A composition according to claim 7 wherein the drying agent is silica gel. 
     
     
       10. A composition according to claim 7 wherein the drying agent is an alkylalkoxysilane wherein m is 3, p is 1 and each of R 7  and R 8  is methyl or ethyl. 
     
     
       11. A method of stabilizing an aryl nitrone-containing composition which comprises maintaining said composition in contact with a drying agent which is substantially inert to said nitrone. 
     
     
       12. A method according to claim 11 wherein said composition also comprises a solvent suitable for use in providing a spin-coatable mixture. 
     
     
       13. A method according to claim 12 wherein the drying agent is a molecular sieve, silica gel or an alkylalkoxysilane of the formula (R 7  O) m  Si(OR 8 ) p , wherein R 7  and R 8  are lower alkyl radicals and m+p=4. 
     
     
       14. A method according to claim 13 wherein said composition also comprises a substantially inert polymeric binder. 
     
     
       15. A method according to claim 14 wherein the aryl nitrone has formula II in the drawings, wherein: Z is (R 3 ) a  --Q--R 4  -- or R 5  ;   Q is a monovalent, divalent or trivalent substituent or linking group;   each of R, R 1 , R 2  and R 3  is independently hydrogen, an alkyl or substituted alkyl radical containing 1-8 carbon atoms or an aromatic radical containing 6-13 carbon atoms;   R 4  is an aromatic radical containing 6-13 carbon atoms;   R 5  is an aromatic heterocyclic radical containing 6-20 carbon atoms in which the hetero atoms are at least one of oxygen, nitrogen and sulfur;   R 6  is an aromatic hydrocarbon radical containing 6-20 carbon atoms;   X is halo, cyano, aliphatic acyl, alkyl or substituted alkyl of 1-8 carbon atoms, aryl of 6-13 carbon atoms or carbalkoxy;   a is from 0 to 2;   b is from 0 to 3; and   n is from 0 to 4.   
     
     
       16. A method according to claim 15 wherein the nitrone is α-(4-diethylaminophenyl)-N-phenylnitrone. 
     
     
       17. A method according to claim 16 wherein the drying agent is a molecular sieve. 
     
     
       18. A method according to claim 16 wherein the drying agent is silica gel. 
     
     
       19. A method according to claim 16 wherein the drying agent is an alkylalkoxysilane wherein m is 3, p is 1 and each of R 7  and R 8  is methyl or ethyl. 
     
     
       20. A method according to claim 15 wherein said drying agent is enclosed in a liquid-permeable container.